On-vehicle display

ABSTRACT

An on-vehicle display used in automotive vehicles for displaying an image projected from within a dashboard of a vehicle. A first reflecting surface on a windshield of a vehicle. The first reflecting surface is at a first angle with the dashboard. A second reflecting surface on a reflector is mounted in the proximity to a lower end portion of the windshield. The second reflecting surface is at a lower position than the first reflecting surface and at a second angle with the dashboard. A vehicle speed sensor for outputting a vehicle speed signal indicative of said vehicle speed to said controller. A controller guides the image projected from within the dashboard either to the first reflecting surface or to the second reflecting surface depending on a vehicle speed. A photodetector outputs a light intensity signal indicative of an intensity of ambient light in the proximity to the windshield. A controller receives the light intensity signal from the photodetector and guides the image projected from within the dashboard to the second reflecting surface when the light intensity signal is outside a predetermined range.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display used for vehicles and moreparticularly to a display for indicating information such as vehiclespeed to the driver, which information exists as a virtual imageappearing at a distance from the driver's eyes.

2. Prior art

Many of conventional on-vehicle displays used for automotive vehiclesare installed, for example, under the dashboard of the vehicle so thatthe displays are out of the driver's sight while the driver is drivingthe vehicle. While driving the vehicle, the driver's eyes move mostly inthe horizontal direction since the driver is watching for oncomingtraffic. However, the driver has to move his or her eyes verticallywhenever the driver wishes to look at, for example, the speedometerunder the dashboard. This is inconvenient particularly when the vehicleis running at relatively high speeds, and becomes increasinglyinconvenient as the vehicle speed increases. One way of solving theaforementioned problem is to employ a head-up display where an imageindicative of driving information is within the driver's sight while thedriver is driving the vehicle. The image is viewed within the driver'ssight but at a distance from the driver's eyes so that the driver needsto move his eyes only by small angles.

As shown in FIG. 6, Japanese Patent Preliminary Publication No.60-192912 discloses an on-vehicle display for use in automotivevehicles. A projector 1 projects an image indicative of vehicleinformation, e.g., vehicle speed, onto a mirror 2b which in turnreflects the image to the inner surface of a windshield 3 through anopening 4a in a dashboard 4. The windshield 3 then reflects the lightinto the driver's eyes E1 so that the driver views a virtual image X1 ata distance behind the windshield 3. A motor 2a drives the mirror 2b toadjust inclination of the mirror 2 so that the position of the virtualimage may be adjusted between position X1 and X2. However, not only theposition of the virtual image is vertically moved only a little but alsothe image may often be out of the driver's eye range so that the drivermust move his/her eyes to E2 to view the image X2. Therefore, the driverhas to change his or her position in order to view the virtual images X1and X2.

Sometimes, head-up displays are not advantageous, particularly on a fineday, in that small differences in intensity between the ambient lightand the virtual image results in poor contrast of the virtual image.Moreover, the virtual image appears in the driver's sight when thevehicle is running at high speeds. This disturbs the driver's sight. Theimage tends to be reflected by both the outer surface and inner surfaceof the windshield 3 at night so that the display image may often bedual, resulting in poor display quality.

SUMMARY OF THE INVENTION

The present invention was made in view of the aforementioneddeficiencies. An object of the present invention is to provide anon-vehicle display for use in automotive vehicles where the position ofvirtual image is shifted according to vehicle speed. Another object ofthe invention is to provide an on-vehicle display for use in automotivevehicles where the position of virtual image is shifted according to theintensity of light outside the vehicle.

A reflector is provided near a lower end of the windshield of thevehicle. The reflector or the windshield reflects a display image from aprojector or a fluorescent display, which is located under thedashboard, into the driver's eyes. The driver views the display image asa virtual image either behind the mirror or behind the windshield. Thevirtual image is at higher positions when it is behind the windshieldthan when it is behind the reflector. The reflector is made of, forexample, a dark, opaque material or a reflecting material applied withopaque printing thereon except the reflecting surface.

A controller controls the vertical position of the virtual image so thatthe virtual image is viewed at higher positions behind the windshieldwhen the vehicle is running at higher speeds, and is viewed at lowerpositions behind the reflector when the vehicle is running at lowerspeeds. In addition, the controller controls the position of the virtualimage so that the virtual image is viewed at lower positions behind thereflector when the intensity of ambient light is outside a predeterminedrange, i.e., during the daytime on a very fine day or during the night,in which case, the virtual image may be viewed at lower positions behindthe reflector irrespective of the vehicle speed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and other objects of the invention will become more apparentfrom the description of the preferred embodiments with reference to theaccompanying drawings in which:

FIG. 1 illustrates an embodiment of an on-vehicle display according tothe present invention;

FIG. 2 illustrates another embodiment of the invention;

FIG. 3 illustrates a photodetector used in the present invention fordetecting the intensity of ambient light;

FIG. 4 illustrates the visibility of the driver while the driver isdriving the vehicle;

FIG. 5 is a flowchart showing the sequence for controlling the positionof virtual image; and

FIG. 6 illustrates a prior art on-vehicle display.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Construction

In FIG. 4, a horizontal line h1 passes through point P1 in the eye rangeof a driver and a horizontal line h2 passes through point P2. PositionS1 is where a line at a depression angle of five degrees with thehorizontal line h1 intersects the windshield 3. Position S2 is where aline at an elevation angle of seven degrees with the horizontal line h2intersects the windshield 3. Region B bounded by positions S1 and S2must be cleared from any obstructions so that the driver is able todrive the vehicle safely.

Position S3 is where a line at a depression angle of one degree with thehorizontal line h1 intersects the windshield 3. Position S4 is where aline at an elevation angle of three degrees with the horizontal line h2intersects the windshield 3. Japanese Industrial Standards require thatno display image is reflected by region A bounded by positions S3 andS4.

The invention will be described in detail with reference to thedrawings. FIG. 1 shows an embodiment of a head-up type display for usein automotive vehicles according to the invention. There are provided aprojector 1, rotatable mirror 2, and controller 10, all of which arelocated under a dashboard 4. The controller 10 includes a manual switch7, speed sensor 6 that outputs a vehicle speed signal, electroniccircuit 8 having a CPU, and a drive circuit 9 that drives the motor 2ain accordance with the output of the electronic circuit 8. The rotatablemirror 2 includes a motor 2a and a mirror 2b. The manual switch 7includes, for example, two switches; one is an up switch and the otheris a down switch (not shown.) A continuous press of the up switch causesthe motor 2a to drive the mirror 2b so that the virtual image appears athigher positions. A continuous press of the down switch causes the motor2a to drive the mirror 2b so that the virtual image appears at lowerpositions.

The projector 1 projects a display image indicative of vehicleinformation, such as vehicle speed, onto the mirror 2b. The mirror 2breflects the display image from the projector 1 through an opening 4aeither to the reflector 5 or to the windshield 3. The electronic circuit8 receives the vehicle speed signal from the speed sensor 6 and controlsthe drive circuit 9 in order to tilt the mirror 2b in accordance withthe vehicle speed signal. The electronic circuit 8 also provides asignal representative of vehicle speed to the projector 1. Tilting themirror 2b causes the light incident thereto to be reflected at differentincident angles and reflection angles.

When the mirror 2b is at position B in FIG. 1, the mirror 2b reflectsthe display image L1, projected by the projector 1 to the reflector 5,through the opening 4a in the dashboard 4. The light L1 is thenreflected as a light L2 into the driver's eyes E. The driver sees avirtual image X1 at a low position behind the reflector 5.

When the mirror 2b is at position A in FIG. 1, the mirror 2b reflectsthe display image L3, projected by the projector 1 to the windshield 3,through the opening 4a in the dashboard 4. The light L3 is thenreflected as a light L4 by the inner surface of the windshield 3, andenters the driver's eyes E. The driver sees a virtual image X2 at ahigher position behind the windshield 3. The virtual image X2 isslightly more distant from the driver's eyes E than virtual image X1.The driver is able to see both images X1 and X2 while sitting at thesame position.

The driver views the virtual image X1 at lower positions when thevehicle speed is below a predetermined value, and the virtual image X2at higher positions when the vehicle speed is over the predeterminedvalue. The reflector 5 is provided at a predetermined angle θ withrespect to the dashboard 4 near a lower portion of the windshield 3. Thereflector may be made of a dark, opaque material or a reflectingmaterial with opaque printing applied thereon except the reflectingsurface.

The controller 10 may be designed to gradually vary the position ofvirtual image behind the reflector 5 or windshield 3 so that the virtualimage is at lower positions when the vehicle is running at lower speedsand at higher positions when the vehicle is running at higher speeds.

Alternatively, the motor 2a can be manually operated, whereby shiftingthe manual switch 7 causes the motor 2a to be manually controlled todrive the mirror 2, thereby allowing the driver to show the virtualimage at a desired position. On the other hand, position of the displayimage may be stored in a memory in the electronic circuit 8 so that thedisplay image may automatically appear at the predetermined positionwhenever the display apparatus is turned on. The head up displayaccording to the invention is designed so that the display image willnever appear bridging between the windshield and the reflector 5.

A photodetector 12, as shown in FIG. 3, may be provided on the dashboard4, as shown in FIG. 1, where ambient light enters through the windshield3 and provides a light intensity signal indicative of the intensity ofambient light to the electronic circuit 8. The electronic circuit 8examines the light intensity signal to determine whether the brightnessoutside the vehicle is within or outside a predetermined range. If thebrightness is outside the predetermined range. i.e., during the nightwhen it is very dark or during the daytime when it is very bright, thevirtual image is formed behind the reflector 5 irrespective of thevehicle speed. Forming a virtual image behind the reflector rather thanbehind the windshield eliminates the tendency of dual images due toreflection by the outer and inner surfaces of the windshield at night.

FIG. 2 shows another embodiment of an on-vehicle display apparatusaccording to the invention. The on-vehicle display is the same as thatin FIG. 1 except that the projector 1, the mirror 2a, and the motor 2bare replaced by a fluorescent image display 1I. Elements similar tothose in FIG. 1 have been given the same reference numerals. In FIG. 2,a drive circuit 9 controls a motor 11a to drive a fluorescent imagedisplay 11, so that a light emitting surface lib is tilted with respectto the windshield 3. The image projected from the light emitting surface11b is in the form a divergent bundle of rays which are reflected notonly by the reflector 5 but also by the windshield 3. Thus, the lightemitting surface 11b has placed thereon a light control film 11c, whichgives a predetermined direction to the rays. The image projected fromthe light emitting surface 11b is reflected by the inner surface of thewindshield 3 behind which a virtual image X2 is formed at relativelyhigh positions, or is reflected by the reflector 5 behind which avirtual image X1 is formed at relatively low positions. Of course, thelight emitted from the display 11 may be reflected by a mirror (notshown) which, in turn, reflects the light to the windshield or thereflector 5. The photodetector 12 in FIG. 3 may also be used in theembodiment shown in FIG. 2.

The embodiment in FIG. 2 operates in a similar manner to that in FIG. 1.When the display 11 is at position C, the driver sees the image X1. Whenthe display 11 is at position D, the driver sees the image X2.

In the embodiments in FIGS. 1 and 2 and with reference to FIG. 4, thereflector 5 is mounted at an area lower than point S1 at an angle θ withthe dashboard 4. The inclination of mirror 2 is controlled so that thedisplay image is reflected either by the inner surface of the windshieldin the area between points S1 and S3 in FIG. 4 or by the reflector 5according to the vehicle speed and ambient light intensity. Thus, thedisplayed image will not disturb the driver's visibility during driving.

The operation of the controller 10 in FIG. 1 will be described withreference to the flowchart in FIG. 5. It is assumed that the on-vehicledisplay apparatus includes the photodetector 12. The program in FIG. 5starts when the driver turns on the engine. At step S1, a random accessmemory (referred to as RAM hereinafter) in an electronic circuit 8stores the vehicle speed signal outputted from the vehicle speed sensor6. At step S2, the RAM also stores the light intensity signal indicativeof the intensity of ambient light outside the vehicle. At step S3, thevehicle speed signal is read from the RAM and is compared with apredetermined threshold value. If the answer is NO at step S3, theprogram proceeds to step S5. If the answer is YES at step S3, then theprogram proceeds to step 54 where the light intensity signal is readfrom the RAM and a check is made to determine whether the lightintensity is outside a predetermined range. If the answer is YES at stepS4, the program proceeds to step S5 where the controller 10 controls themotor 2a to drive the mirror 2b to tilt so that the virtual image X1 isformed at a lower position. If the answer is NO at step S4, the programproceeds to step S6 where the controller 10 controls the motor 2a todrive the mirror 2b to tilt so that the virtual image X2 is formed at ahigher position somewhat closer to the driver than the virtual image X1.The virtual images X1 and X2 are about 0-10 millimeters away from eachother relative to the driver's eyes depending on their positions.

At steps S1 and S2, the vehicle speed and ambient light intensityoutside the vehicle are actually periodically measured. The position ofthe mirror is adjusted each time the vehicle speed and ambient lightintensity are measured, so that the position of the virtual image isupdated periodically at step S4, the drive circuit 9 examines the lightintensity signal from the light sensor 12 to determine whether it is thedaytime on a very fine day, or it is a night when the intensity ofambient light is nearly zero. When the light intensity signal is of avalue in the range from nearly zero to a predetermined value, thecontroller 10 drives the mirror 2b in accordance with the vehicle signalso as to form the virtual image at high positions or low positionscorrespondingly. On the other hand, the virtual image is at lowerpositions even though the vehicle is running at high speeds, if thelight intensity signal is not in the range from nearly zero to thepredetermined value.

The opening 4a in the dashboard 4 may be closed with a transparent glassplate or a transparent resin board to protect from dust.

What is claimed is:
 1. An on-vehicle display for displaying an imageprojected from within a dashboard of a vehicle, comprising:a windshield;a first reflecting surface defined by a lower end portion of the innersurface of the windshield, said first reflecting surface being operativeto reflect an image projected from within the dashboard into a driver'seyes when the image falls on said first reflecting surface; and a secondreflecting surface being fixed with respect to said windshield at aposition lower than said first reflecting surface, said secondreflecting surface being angularly displaced with respect to said firstreflecting surface and being operative to reflect an image projectedfrom within the dashboard into the driver's eyes when the image falls onsaid second reflecting surface; angularly adjustable image projectingmeans for projecting an image onto said first reflecting surface or saidsecond reflecting surface, a light sensor; and a controller operativeduring a predetermined set of light conditions, as determined by saidlight sensor, to vary the disposition of said image projecting means todirect said image to various positions on said first reflecting surfacewhen said vehicle operates over a higher range of speeds and to directsaid image to various positions on said second reflecting surface whensaid vehicle operates over a range of speeds lower than said higherrange of speeds; said controller including means operated in response tosaid light sensor to restrict the disposition of said image projectingmeans to direct said image to various positions on said secondreflecting surface over the entire range of vehicle speeds when saidlight conditions are outside of said predetermined set of conditions;wherein the driver views a virtual image of the image projected fromwithin the dashboard behind said first reflecting surface or said secondreflecting surface.
 2. An on-vehicle display according to claim 1,wherein said controller includes a vehicle speed sensor for outputting avehicle speed signal indicative of said vehicle speed to said controllerso that said controller guides the image projected from within thedashboard either to said first reflecting surface or to said secondreflecting surface depending on a vehicle speed.
 3. An on-vehicledisplay according to claim 2, wherein said controller controls movementof said image projecting means to guide the image projected from withinthe dashboard either to said first reflecting surface under a firstvehicle operating condition in which the vehicle speed signal is higherthan a predetermined value, and to said second reflecting surface undera second vehicle operating condition in which the vehicle speed signalis equal to or lower than the predetermined value.
 4. Anon-vehicledisplay according to claim 3 in which said light sensor comprises aphotodetector for outputting a light intensity signal indicative of anintensity of ambient light coming into the vehicle through thewindshield, and said controller receives the light intensity signal fromsaid photodetector and controls the movement of said image projectingmeans to project the image projected from within the dashboard to saidfirst and second reflecting surfaces when the light intensity signal iswithin a predetermined range and to only said second reflecting surfacewhen the light intensity signal is outside said predetermined range. 5.An on-vehicle display according to claim any one of claims 1, 3 and 4further including a manual switch for manually causing said controllerto control the movement of said image projecting means to project theimage either onto said first reflecting surface or onto said secondreflecting surface.